As the last visitors left Warsaw's Museum of Strange Inventions and the lights in the halls began to dim, Adam and Lena stayed in the lobby for a while longer. They were both members of the Young Explorers Club, and tonight, exceptionally, they were allowed to spend the night at the museum as part of a scientific adventure. Although they feigned composure, inside they were bubbling with excitement. Adam was fourteen, always wore oversized sweatshirts and collected all sorts of unusual gadgets. Lena, a year older, was interested in robotics and loved to take apart anything that fell into her hands. They were to spend the whole night under the watchful eye of Mr Falcon, the club's caretaker, who, however, had a habit of falling asleep a few minutes after putting his head to the pillow. The museum was a place full of bizarre exhibits: typewriters that rewrote old novels by themselves, clocks with moving birds and even light bulbs that lit up to the rhythm of visitors' voices. However, it was only after dark that something truly extraordinary happened here. As the museum quietened down, Adam and Lena spread out their sleeping bags just inside the entrance to the Hall of Shadows - the room that housed the oldest inventions. Lena could not fall asleep. Instead, she stared at the closed door with its brass handle gleaming in the night light. Suddenly, she heard a quiet knocking. "It must be the wind," she thought, but Adam was already sitting upright, with his ear to the ground. - 'Do you hear that? - He whispered excitedly. The tapping suddenly quietened down, but a squeaky voice immediately followed, so quiet it could barely be heard: - Hello? Is anyone there? Adam abruptly pushed back his sleeping bag, and Lena rolled over onto her knees. The voice came from under an old cast-iron telephone standing on a table in the corner. The phone, still remembering pre-war times, slowly moved the dial and blinked a red light. - Answer the receiver! - asked the phone with obvious anxiety. Lena looked at Adam as if asking if he was dreaming. Adam, however, was already at the table and picked up the receiver. At the same moment, the door of the Shadow Room creaked wide, and from inside the mist oozing across the floor took the shape of a strangely familiar umbrella. An umbrella that smiled broadly showing, surprisingly, porcelain teeth. - Follow me, children," the umbrella called back in a rustling voice, "tonight everything will change.... Adam and Lena exchanged glances full of disbelief, but before they could speak, more voices began to echo throughout the museum. A typewriter tapped out a message on yellowed paper, clocks punched out the wrong time as usual, and a carved armchair bounced against the wall as if inviting someone in. The umbrella moved through the mist further and further into the Shadow Room. Adam tried to say something, but his voice trapped in his throat. Lena squeezed his hand and said in a whisper: - I think we need to find out what's going on here. They took a deep breath and moved cautiously behind the umbrella, leaving their sleeping bags and guardian plunged behind them. Just before they entered the hall, they suddenly heard a loud crash and all the lights in the museum went out....